1. Field of the Invention
The present invention relates to a method for preforming of two or more integrated connectorless flexible cables in flexible sections of a rigid-flex printed circuit board consisting of a combination of rigid printed circuit board sections and flexible printed circuit board sections extending therebetween. Moreover, the invention is also directed to an apparatus for the preforming of two or more integrated connectorless flexible cables in flexible sections of a rigid-flex printed circuit board consisting of a combination of rigid printed circuit board sections and therewith interposed flexible printed circuit board sections which are adapted to interconnect the rigid printed circuit board sections.
In the electronic packaging industry, there are provided operatively joined wherein pluralities of rigid printed circuit board (PCB) sections which are essentially interconnected through the intermediary of flexible printed circuit board sections. In the case of numerous physical instances and applications, these combinations of rigid printed circuit board sections and flexible printed circuit board sections, referred to as rigid-flex printed circuit boards, are employed in order to solve three-dimensional space problems, reduce electrical noise by eliminating connectors and reducing the overall area of the printed circuit board. Basically, the flexible printed circuit board sections enable the therewith joined rigid printed circuit board sections to be folded and unfolded relative to each other through predetermined angular displacements, normally, although not necessarily angled, in 90° segments, 180° segments, or any arbitrary angle greater than 0° up to 180°, in order to form a three-dimensional printed circuit board structure.
Generally, in order to interconnect pluralities of printed circuit boards with each other, there are presently employed connectors and cables with connectors on each end, as is well known in the electronic packaging industry. However, the uses of such connectors are subject to limitations and disadvantages, in that these connectors add an expense to the printed circuit board structures, the connectors frequently cause electrical noise in the utilization of the electronic packages in which the printed circuit boards are installed, and moreover, such connectors represent points of failure in the overall packaging system. Consequently, it is highly desirable to provide a rigid-flex printed circuit board which combines rigid printed circuit board sections and flexible printed circuit board sections which extend therebetween in order to provide three-dimensional printed circuit board structures in which the presently employed connectors are eliminated, thereby substantially obviating or at least considerably ameliorating all of the foregoing limitations and drawbacks. Specifically, the rigid printed circuit board sections are for component and hardware placement. The flexible printed circuit board sections provide for three-dimensional forming, thereby eliminating the requirement for board-to-board connectors. The elimination of these unnecessary connectors frees up valuable surface area for hardware and component placement or reduces the size and cost of the rigid-flex printed circuit board.
In current rigid-flex printed circuit board constructions, wherein at least two or more rigid printed circuit board sections are operatively interconnected through the intermediary of flexible printed circuit board sections comprised of two integrated connectorless cables, the flexible printed circuit board sections are folded so as to, for example provide a 90° or a 180° angled construction. The rigid-flex printed circuit board structure is assembled in a two-dimensional or flat state, electrically tested, folded into a three-dimensional state, electrically retested at the location of the assembly supplier, and then inserted into a suitable bottom sheet metal cover comprising a protector. However, if a rigid-flex printed circuit board fails subsequent to electrical retesting thereof, then the assembly supplier unfolds the entire rigid-flex printed circuit board electronic package for reworking.
The foregoing folding and subsequent unfolding from two-dimensions and three-dimensions, and conversely, may frequently cause an early life conductor fatigue failure in the integrated connectorless flexible cables contained within the flexible printed circuit board sections of the rigid-flex printed circuit board structure. Consequently, such operations necessitating folding and unfolding cycles may, at times, due to breakage of one or more conductors caused by fatigue failure, result in having to permanently scrap extremely expensive rigid-flex printed circuit board structures.
In view of the foregoing, it is of importance in the electronic packaging industry to be able to provide for of rigid-flex printed circuit boards with flexible printed circuit board sections which interconnect various rigid printed circuit board sections, whereby problems of flexing the integrated connectorless flexible cable sections do not lead to an early fatigue and failure of the conductors within the flexible printed circuit board sections between the rigid printed circuit board sections.
2. Discussion of the Prior Art
Although the technology has addressed itself to various methods and types of apparatus for controlling bends and flexure in cables extending rigid connecting structures, these have not fully considered the problem addressed by the present invention.
Farrow, et al. U.S. Pat. No. 6,166,332 discloses a method and apparatus for securing a ribbon cable in a bent position, wherein the ribbon cable is maintained in a cable clamping apparatus while being kept from interfering with the electrical conduction of the cable. In particular, the clamping apparatus merely maintains a central point of the cable in a predetermined bent position for electrical testing. There is no consideration as disclosed by the present invention for preforming two or more parallel flexible cable sections which are subjected to two-dimensional and three-dimensional folding and unfolding to accommodate the orientation of printed circuit boards to which the flexible cables are attached. Consequently, this patent does not address itself to and has nothing in common with the present invention.
Nishikigi U.S. Pat. No. 5,951,322 provides for the bending of a flat cable connection structure to obtain strain relief to be able to impart a bend thereto without imparting any excessive stresses thereto. This type of construction does not pertain to multiple flexible layer cable sections which are adapted to be folded in angled segments to form a three-dimensional printed circuit board. Again, this patent has nothing in common with the present invention.
Nishitani et al. U.S. Pat. No. 5,877,936 discloses an expansion structure for door-mounted electrical circuit bodies, wherein an electrical cable is adapted to be folded in loops such that door structures which extend are able to stretch or, alternatively, fold the cable loop within a guide protector. The contraction of the circuit body and expansion thereof responsive to closing or opening of a door has nothing in common with imparting a preformed configuration to a flexible cable section intermediate rigid printed circuit boards adapted to prevent any potential damage to copper or metallic layers within the flexible cable.
Hayakawa et al. U.S. Pat. No. 5,446,240 discloses the flexing of a flexible cable structure to prevent undue deformation thereof, and to form various loop configurations during flexing and twisting through bending of opposite side portions of an intermediate length of cable. This patent does not address itself to the particular problems solved by the present invention.
Uemori U.S. Pat. No. 4,987,422 discloses a wiring device in which a ribbon cable is provided in a loop and in a C-shaped section adapted to be pulled in a manner whereby a movable portion is displaced relative to an immovable portion or member of the cable. This has nothing in common with the inventive concept.
Purdy et al. U.S. Pat. No. 4,660,125 discloses a ribbon cable assembly whereby the latter is adapted to be folded or unfolded in conjunction with the movement of the pull-out draw of an electronic equipment cabinet. Again, this has nothing in common with the particular invention as described herein.
Dryg U.S. Pat. No. 3,647,936 basically describes a self folding cable carrier in which the extension of a drawer unfolds a plurality of loops of flexible cable, and upon closing of the drawer, the flexible cable will slide back in to a tight loop-forming arrangement. This has nothing in common with the present invention.
Erdle U.S. Pat. No. 3,459,880 discloses a flexible bus bar with S-shaped cable sections which are adapted to be conveyed across a system of rollers to compensate for movements of a cabinet door. This has nothing in common with the inventive construction.
Turner, Jr. U.S. Pat. No. 3,027,417 discloses an extensible electrical cable which is adapted to be slid out from an inter-engaged telescoped coiled position into an axial extension by being unwound along a longitudinal axis.
Francis U.S. Pat. No. 2,902,535 merely discloses a prefolded card which may be wound over retaining rod-shaped holders in a continuous multi-loop like configuration.
Finally, Weimer U.S. Pat. No. 457,687 discloses an electric light hanger in which a coiled electrical cable is adapted to be extended or retracted relative to a base support structure.